Refrigerating apparatus



Oct. 5, 1937. l

L. A. PHlLlPP Filed April 15, 1932 REFRIGERAT ING APPARATUS 2 Sheets-sheet 1 AMg INVENTOR.

11W/asma' 4. PML/'PP W e. um Y ATTORNEY,

ct. 5, 1937. l.. A. PHlLlPP REFRIGERATING APPARATUS Filed April 15, 1952 2 Sheets-Sheet 2 INVENTOR. 0h/RAME li. PII/IPP ATTORNEY.

Patented Oct. 5, 1937 UNITED STATI-:s PATENT OFFICE nEFnIGEnA'r'rNG APPARATUS Lawrence A. Philipp, Detroit, Mich., assigner. by

mesne assignments,

to Nash-Kelvinator Corporation, Detroit, Mich., a corporation of Mary- Application anni` 1s, 1932, serial No. 605,465

31 claims. (ci. ca -115) f This invention relates to refrigeration and more particularly to an improved method and apparatus for controlling temperatures.

One of the objects of my invention is to prol an improved method of controlling temperatures l in the primary and secondary systems of the aforesaid apparatus. l

A further object .of my invention is to provide a refrigerating apparatus of the vtype which in-y cludes an intermittently operated primary refrigerating system and Va secondaryy refrigeratlng system arranged in heat exchange relation, with the primary system for condensing evaporated refrigerant in the secondary Asystem and an lmproved arrangement for controlling the operation of the primary system.

A still further object consists in an apparatus for cooling liquids and the provision of improved means for preventing'the freezing of the liquids during normal or abnormal operation of the apparatus.

Further objects and advantages of the present invention will be apparent from the following description, reference being had tothe accompanying drawings, wherein a preferred form ofthe present invention is clearly shown.

In the drawings: I Fig. 1 is a diagrammatic illustration of a refrigerating apparatus for cooling circulating water, embodying features of my invention;

Fig. 2 is a front view in elevation of a refrigerating apparatus embodying features of my invention;

Fig. 3 is an'enlarged view in cross section taken along the line 3 3 of Fig. 2;

Fig. 4 is a view in cross section of a modified form of refrigerating apparatus; and

Fig. 5 is a diagrammatic illustration of my improved refrigerating system in connection with a soda fountain.

In providing a refrigerating apparatus for cooling circulating water for\drinking purposes, it-

has vbeen found that somey means should be provided for maintaining the element which cools the circulating water within a certain tempera.-

Asystem'.

ture range so that the water may be cooled to the desired temperature at which it is palatable and also so that the temperature of the water is not reduced to a temperature which would cause the freezing thereof'and the possible destruction of 5 the apparatus. In water coolers of the`type which include an intermittently operated refrigeratingA apparatus for cooling the circulating water it has been found by experience that the various types of mechanism employed for controlling the opera; 10 tion of the apparatus or for controlling the admissionof refrigerant to the cooling element of the apparatus are very likely to become faulty inV operation which causes abnormal operation of the apparatus. It has also been found thatl the con- 15 trolling mechanisms are very\ likely to get out of proper adjustment or that theyare improperly adjusted by someone unfamiliar with the operation of the apparatus. This abnormal operation of the apparatus either results in the drink 20 ing water not being cooled sufficiently or that it is cooled to the point which causes freezing thereof and the Aconsequential destruction of the AIn accordance with my invention I make provisions for maintaining the temperature of the water substantially constant and at' the desired temperature which is labove the freezing point of water. This is accomplished` by providing a refrigeratingapparatus of the type having primary 30 and secondary refrigeratlng systems arranged in heat exchange'relation, .with the primary system ybeing employed for condensing evaporated refrigerant in the secondary system, and the sec ondary system being used for cooling the circu- 35 lating water. In order tocontrol the temperature in the secondary system I have provided in the secondary system a body of liquid, preferably water, congealable by the evaporation of refrigv erant in the secondary system. This congealable 40 liquid is so arranged in the secondary system that the evaporated refrigerant must vpass therethrough before being condensed by the cooling action of the primary system. By this arrangement, the body of liquid gradually becomes con- 45 gealed and when in this form limits the amount of evaporated refrigerant passing therethrough to be' condensed by the primary system. When this takes place, some of the evaporated refrigerant in the secondary system is condensed by the 50` body of liquid in its congealed form. By limiting the amount of refrigerant condensed by the primary system and by serving as a condenser for some of the vaporized refrigerant, the body of water never becomes frozen into a solid mass but 55' 'remains either-mv the form of a liquid or in the form of slush. Since the body of water in vthev secondary system which is .cooled'by the vsecondutilized for cooling circulating air in the i'ood l frosting the element which coolslthe circulating ary system never freezes into a complete solid, it necessarily follows that the circulating drinking water is always maintained a't a temperature above its freezing point;

My invention is also. applicable to household refrigerators. this embodiment of: the invention the primary system is maintained `within predetermined low temperature limits for freezing ice cubes or the like and the secondary system is storage compartment in the usuall manner.

Preferably the cooling element ofthe secondary system is maintained at atemperature which is above the freezing point of water so'as to prevent the-formation of frost on said element by@ moisture deposited thereon from the circulating air. This avoids the necessity of periodically de- A refrigerating apparatus for cooling circulating water is shown in Fig. 1 diagrammatically represented as including a primary refrigerating system 20 and a secondary refrlgerating system .22 arranged in heat exchange relation with the primary system for condensing .evaporated refrigerant in the secondary system. The primary system comprisesl in general an intermittently operated condensing element 24 and a cooling element 25 which is used for condensing-evap-- orated refrigerantgin the secondary system. The

' secondary system is employed for cooling circulating water which passes through a water cooling coil 21 and comprises ingeneral a vaporizing chamberZB formed by a metallic tank-like member 29. Suitable insulation 3| is interposed between the metallic member 29 and an' outer cover 33. Within the vaporizingcham'ber there is provided a body of liquid refrigerant, the level of which I have indicated at 35,'the water coolingcoil 21 whichds located below the level of refrigerant, cooling element 25'which provides a. condensing zone for evaporated refrigerant, and a body of water, the level of which I have indicated at 31.

ing.r systems to` prevent the freezing of water in coil 21 and also prolongs the off phase of the refrigerating cycle of the intermittently'operated primary system in a manner about to be de- Any suitable condensing element may be used for supplying refrigeration to the cooling ele-v ment 25. As herein shown, I provide a condenser 40, liquid refrigerant receiver 4I, compressor 43,

and motor M for operating compressor 4 3. The compressor 43 withdraws vaporized refrigerant from the .cooling element 25 through a vapor conduit 41', compressesthe gaseous' refrigerant and delivers it to the condcnserilll wherein itis lique` 'ed and from which it passes to receiver 4l.

.Liquid'refrigerant is supplied tothe cooling element 25 through a liquid conduit 49 under the controlof an expansion valve 50. Preferably the expansion valve is thermostatically controlled in accordanceP with changes in temperature within the cooling element `25 by means of thermostat bulb 55 which is located preferably in contact with. the outletend of the cooling element 25.

Preferably the operation of theprimary system is controlled in response to changes in temperature of the body of water within the 'vaporizing 'Ihis body o f water is adapted to maintain a temperature differential between the refrigeratvof Water. Thel switch 6 0 is adapted tocut the motor in and out of circuit with the power mains in accordance with changes in temperature of the-body of water. i

The operation of the device is as follows: Assumingfthat there is a demand for drinking water, some of the cooled water in the coil 21 will flow out of the discharge end 61 of the coil 211and water to be cooled will enter the inlet end 69 of coil 21 at a -temperature higher than that .to which it is to be cooled.v 'Ihe coil 21 may be connected to any suitable pressure system for receiving water-and is of such vsize and shape so that .when the. water enters the coil andpasses therethrough lt will,4 by the time lt is tol leave the water cooling coil, be 'at itsdesirod tem` i perature. This incoming warm water-to be causing some of the refrigerant to boil. When this ebullition takes place, evaporated reflil-'Qlnt must pass through thelbody Vof water before passing tothe cooling 4 elementj25 to be condensed.

This .evaporation of refrigerant causes the'water to gradually become congealed, and in soifdoflng, gradually forms a solid which limits the amount of evaporated "refrigerant which may.. pass throughthis congealed body and consequently limits the amount of condensation which `'taires place in the condensing zone .adjacent thef"coollng element 25. When this takes place, the congealedI body of. water serves as an auxiliary ycondensing medium and condenses some of therefrigerant evaporated in the secondarysyem. This condensing action warms up the congealed l25 cooledgives up its heat to the liquid refrigerant, l

body 'and causes aportion thereof to melt and return to its original form of water, the amount depending upon the amount of ebullition which takes place in the secondary system. Thus it will lbe noted that the evaporation of refrigerant gradually changes t e physical properties` of the v water to a solid. W en this takes place the congealed body closes off the passagewayv for evaporated refrigerant leading .to the cooling element 25 in varying proportions.` -In addition, this congealed body serves as a' condenser for some of the evaporated refrigerant and in yso doing changes the, evaporated refrigerant to a` liquid and converts the congealed body partially oren- .tirely to a liquid. 'This is true whether there are occasional demands .for drinking water or whetherthe evaporation of refrigerant in the of heat fromv the exterior of the water cooling apparatus to the body of liquid refrigerant I5. In view of the fact that thesame body of refriger-v 'ant which cools thebody of water 31 also cools -the drinking water within the coil 21, itfwill be readily seen that the drinking water will not Ibe cooled below its freezing pointeven though there is no demand for drinking water over'an appreciable length of. time.

` Another important advantage in providing a congealable liquid within the secondary system is that the congealedzbody serves as a. hold over which' prolongs the "ofi-phase". of the refrigerating cycle of the primary system. This ls`accomsecondary system takes place dueto the leakage used whichis offa lighter specific gravity than plished by controlling the operation of the primary system in response to changes in temperature in the body of water 31 as previously described herein. In view of the fact that the body of water 31 when in congealed form condenses some of the evaporated refrigerantl in the secondary system, it will be unnecessary to operate the primary system to perform its condensing action as frequently as it would be necessary without the-auxiliary condenser for congealed body of water. Under these conditions, the switch -6D may be set to cut the motor in circuit with the power mains after a major portion or all of the congealed body has returned to its original form of water. It will also be noted that this arrangement permits a wide variation in temperature in the primary system without harm.

Preferably the cooling element 25 of the `pri-` mary system 20 has sufficient capacity to adequately perform its condensing function but issuch that during the oilf phase of the refrigerating cycle of the primary system the element warms up so as to melt or defrost any frost or ice which may be deposited thereon by water vapors in the secondary system. It will also be noted that the warming action of the evaporated refrigerant in the secondary system aids in preventing the formation of ice on the cooling element 25. I

In the apparatus shown in Fig. l, I `prefer to use methylene chloride asvthe refrigerant and a fluid, such as water which has a high heat l capacity for a smallchang'e in temperature, as the congealingjliquid.'l However, it is to be 4uri-- derstood that any refrigerant which does not have a deleterious eifect on the apparatus when used with acongealable body may be used. Likewise` any ysuitable congealable bodyv of liquid may' be that of the refrigerant and'whichis insoluble in the refrigerant.

i In Figs. 2 and 3 of the drawings I have shown my invention in connection with ahousehold re' frigerator designated 15. The refrigerator `15 comprises in general a cabinet 16 having a food l storage compartment T8 formed by an inner me- -ment 24 shown in Fig. 1.

tallic liner 19.` Suitable insulation sucli as cork is interposed between the inner metal liner 19 and outer metallic cover 82. The cabinet 16 is-provded with' an opening -85 in the food storage' compartment 'I8 closed by door 81. Within the food storage compartment there is provided a cooling element which is supplied with re- Y `frigerant by a condensing element not shown but which may be the same as the condensing ele- The cooling element 90 is disposed within 'a vaporizing chamber 94 of a secondary refrigerating system 91 for condensing evaporated refrigerant inthe secondary system. The vaporizing chamber 94 is formed by a finned casting member 99 and a removable front plate |66. Within the vaporizing chamber I have provided a body of liquid refrigerant, preferably methylene chloride, the level of which I have indicated at |02, and above the body of refrigerant I have provided a body of water, the level of which I have indicated at |04. In this particular embodiment, I have arranged the cool- ||l 6 for freezingv ice cubes or the like and have arranged for cooling circulating air in -the food storage compartment 18 by means of the secondary refrigerating system 91. The cool-ing element 90 is preferably of the flooded float controlled type. Any suitable supporting means may for the reception of ice making receptacles H2.

Below the sleeve I I0 and extending into the body of refrigerant |02 in the secondary system, Ihave provided a sleeve H5 which is somewhat larger than the sleeve H0 for the reception of a tray H1. The compartment provided by the sleeve H5 may be used for the storage of food articles at a temperature slightly below the temperature in the compartment 16 and above the temperature in the lfreezing zone |06. Y

.In the apparatus shown in Figs. 2 and 3, the functions .of the water and refrigerant in the secondary system are the same asin the apparatus shown in Fig. l. In this apparatus the refrigerant is evaporated by heat received from the circulating air in the compartment 18.v By properly proportioning the amount of water and refrigerant in the se- .ondary system, any desirable temperaturer differential between. the cooling zones of the prin ary'and secondary systems may be obtained. l

As will be noted in the drawings, the cooling' lelement 90 is entirely insulated from the casting taining low temperatures for freezing ice cubes and 'the like, and the secondary .system may be used for coolingcirculating air within the food storage compartment and that the temperature of the secondary system may be readily maintained at a temperature which provides for properly refrigerating the circulating air but above .the temperature which would cause the freezing of moisture contained inthe circulating air which contacts with the casting 91. This avoids the necessity of periodically defrosting the element' which cools the circulating air.

As shown in Fig. 2, the-cooling' element 96 is provided with 'a liquid supply conduit |20 and a refrigerant vapor conduit |22 for supplying liquid refrigerant to and for withdrawing gaseous refrigerant from the element 96 respectively. In this particular embodiment of the invention, it is desirable that the cooling element 90 produce sufiicient low temperatures for freezing andmaintaining in the frozen condition substances in the trays H2. Consequently it is desirable that the operation of the primary system be controlled in accordance with temperatures prevailing in the cooling element 9|). For this purpose I have provided a conduit .|26 which may be connected to bellows 6|. By this. arrangementV the operation of the primary' system is controlled by changes in pressures in the elemen't 90. Since the cooling element 90 is of the flooded type, changes in pressures and temperatures bear a direct relation with one another. Consequently the operationof the switch 60 in response to changes in pressure within the cooling element 90 will be the vided with an ,-insulated ice cream compartment over |21 and an'insulated vaporizing chamber |30. Within the compartment 21 I-haveA provided a plurality of open top sleeves |32 for nreceiving ice cream containers to be refrigerated. 'I'he sleeves |32 arecooled by a coiled cooling element |34 in contact therewith. The compartment |21 may be i'llled'with a brine solution to provide a -holdprovided a'coil |31. for cooling circulating water, a body of4 liquid refrigerant the level of which I have indicated at |39, a vbody of congealable liquid |4| anda coling element |43 forA condensing evaporated refrigerant in the chamber |30.

The element |43 constitutes the primary system,- and the chamber 30, refrigerant A| 39 and water |4| constitute the secondary refrigerating system. Liquid refrigerantis admitted to the cooling element |43 through conduit |50 under the i primary system so as to maintainpredetermined vlow temperatures for maintainingthe ice creams stored in compartment |21 in a frozen condition,

' I provide for controlling the operation vof the primary system by means of 'a thermostatic bulb' |56 -which ls placed in contact with.-the outlet end of the cooling elementA |34.` This bulb is operatively connected to the bellows 6|- for controlling switch 60.

In Fig. 4 there is shown a modified form of refrigeratingv apparatus for cooling circulating air in household'refrigerators. The apparatus shown in this flgurecomprises in general a cabinet |60 having 'an insulated food storage compartment |62 and an insulated compartment |64. Within the compartment |54 there is disposed the primaryrefrigerating system which is herein shown as a body of solid CO2 |66. An opening |68 is provided in the top wall of the cabinet to permit the insertion ofthe block of solid CO2. The opening |68 is closed by a removable cover |69. With- `in the food storage compartment |62 and extending into the compartment |64 is a secondary refrigerating system |10. 'I'he secondary system comprises in general a u -shapedplate-type member |12 for cooling circulating air within the food' storage compartment |62 and a1 flat plate-type member |14 within the compartment |64. I'he plate-type member |14 is arranged for supporting the block of dry ice so as to provide a good ther.- malv contact therebetween. This portion of the secondary4 refrigerating system constitutes the condenser therefor. 'I'he cooling element |12 and the condensing member |14 of the secondary system are joined by a vertically extending conduit |16 which provides a small riser for evaporated refrigerant in the secondary system.

A quantity of refrigerant such as ether is placed in the cooling element |12 and a lsmall quantity of freezing fluid |82 which is insoluble in the refrigerant is put in the secondary system to ll the riser. When the proper temperature hasbeen reached, the solution freezes and prevents the flow of evaporated refrigerant to the condenser |14 until the cooling element |12 warms Within thev vaporizing chamber |30 I have vis desired to provide up sufficiently to melt the freezing solution.

Thus it will benoted in this embodiment of my inventionthat I have provided a freezing solution within the secondary system which entirely closes oil' the passageway'i'rom the evaporating zone to the condensing zone. If desired, a cooling element similar to the element shown in Fig. 3 may be substituted'for the dry'ice |06 for condensing the evaporated refrigerant in the secondary system when it is desired to make prov ision for freezingice cubes or the" like or when it an automatically operated system.

primary refrigerating Although only preferred forms. of the invention have been illustrated, and those forms described in detail, it-will be apparent to those skilled in the art that various modifications may be made therein without departing from the spirit of the invention or from claims.

`What is claimed is as follows:

1. The process of refrigeration which consists in evaporating and condensing a refrigerant in a closed systemcontaining a bodyofliquid conlgealable and substantially unvaporizable at temperatures prevailing therein and utilizing the latent heat of fusion of the body of liquid when in acongealed'forr'n for condensing the vaporized refrigerant.

2. The process of refrigeration which .consists in evaporating a volatile liquid refrigerant,.con-

.tacting the liquid refrigerant with a body of iluid for congealing the fluid and subsequently utiliz'- ing the latent heat of fusion of the congealed body for condensing the vaporized refrigerant. 3. 'I'he process of refrigeration in a closed system which consists in evaporating a portion of a body of refrigerant, congealing a body of fluid within the system by such evaporation and subsequently utilizing the latent heat of fusion of the congealed body'for condensing the vaporized refrigerant.

4. A closed refrigerating system comprising'a vaporizing chamber containing a quantity oi' volatile refrigerant, means forj condensing refrigera'nt evaporated in said chamber, and auxiliary condensing means for the evaporated Arefrigerant comprisingv frozen liquid within the vapor. izing `chamber congealed by evaporation an'd condensation of refrigerant in said chamber.

5. A refrigeratingsystem comprising a vaporizing chamber containing aquantity of volatile refrigerant, means for condensing refrigerantA evaporated in said chamber, and a body of liquid of lighter specific gravity than said volatile rethe scope of the appended'v frigerant within said4 chamber and congealable by evaporation 'of the refrigerant for controlling the amount of evaporated refrigerant condensed by said means. 1

6. A refrigerating system comprising a vaporizing chamber containing a quantity of. volatile refrigerant, a body of liquid of lighter specific gravity in said chamber and congealable Vby evaporation of said refrigerant, and means above said body of liquid for condensing evaporated refrigerant. l

7. A refrigerating system comprising means providing a chamber adapted to contain a quan- I tity of volatile refrigerant, a body of water floating on top of the liquid refrigerant, and means for condensing evaporated refrigerant which passes through said body of water.

8. The process of refrigeration in a closed flow system which consists in establishing an evaporating zone and a condensing zone in open communicationgwith one another, and controlling the temperature of the evaporating zone by intermittently interrupting the flow of evaporated refrigerant from the evaporating zone.

9. A refrigerating apparatus comprising a primary refrigerating medium including a cooling zone, a secondary refrigerating system in heat exchange relation with said cooling zone for condensing evaporated refrigerant in the secondary system, and a congealable body of fluid immiscible with the refrigerant for controlling the evaporation of the refrigerant in the secondary system.

10. A. refrigerating apparatus comprising aA primary refrigerating system including a cooling zone, a secondary `refrigeratin'g system in heat exchange relationwithv said cooling zone for condensing evaporated refrigerant in the secondary system, and a liquid in said secondary system adapted to become congealed byevaporation of said refrigerant and adapted to condense evaporated refrigerant after congelation of the liquid.

1l. A refrigerating apparatus comprising a primary refrigerating system including ay cooling zone, a secondary refrigerating system including a cooling zone and a portion in heat transfer relation with the cooling zone of the primary system for condensing evaporated refrigerant in said secondary system, and a body of fluid kimrniscible with said refrigerant 4and congealable at temperatures prevailing in said apparatusfor maintaining a temperature differential between said cooling zones.

l2. A refrigerating apparatus comprising a primary refrigerating system including a cooling zone, a secondary refrigerating system including a cooling zone anda portion in heat transfer relation with the cooling zoneof the primary system for condensing evaporated refrigerant in said secondary system, and a congealable liquid in the secondary system of lighter-specific gravity than said refrigerant for maintaining a temperature differential between said cooling zones.

13. A refrigerating apparatus comprising an vintermittently operated primary refrigerating system including a cooling zone, a secondary refrigerating system in heat exchange relation with said cooling zone for condensing evaporated refrigerant in the secondary system, said secondary system including a cooling zone, a'body of fluid congealable at temperatures prevailing in the apparatus for controlling the flow `of evaporated refrigerant in the secondary system to the cooling zone of the primary system, and

means responsive to. changes in temperature of i said body for controlling the operation of said primary system.

14. A refrigerating apparatus comprising an intermittently operated primary refrigerating system including a cooling zone, a secondary refrigerating system in heat exchange relation with said cooling zone for condensing evaporated refrigerant in the secondary system, said secondary system including a cooling zone, a body of liquid congealable by the evaporation of refrigerant in the secondary system for controlling thev flow4 of evaporated refrigerant in the secondary system to the cooling zone of the primary system, and means responsive to changes in temperature in said primary cooling zone for controlling the operation of said pimary system.

15. Refrigerating apparatus comprising, in combination, a primary refrigerating system including a cooling element, and a secondary refrigerating system disposed in heat transfer -relation to the primary system for condensing evaporated refrigerant in the secondary system, said secondary systemy including a quantity of volatile refrigerant and a body4 of congealable liquid which is nonmiscible with said volatile refrigerating for maintaining a'temperature differential between the primary and secondary systems. 'Y

16. A refrigerating system including a condensing zone and an evaporating zone, aquantity of volatile refrigerant-'disposed in said evaporating zone, and av body of Water floating on the surface of said refrigerant. i- 4 17. Asecondary refrigerating .system including a condensing zone and an evaporating zone, a quantity of volatile refrigerant disposed in said evaporating zone, and a body of congealable liquid which is nonmiscible with the refrigerant.

floating on the surface of the refrigerant to vary the temperatures between the condensing and evaporating zones.

18. Refrigeratng apparatus comprising, in-

combination, a tankA containing a quantity of liquid refrigerant and 'a body of liquid in contact with the refrigerant and congealable by evaporation of said refrigerant, and a cooling element for condensing the-evaporated refrigerant.

19. Refrigerating apparatus comprising heat absorbing means adaptedto be placed in a refrigerator for cooling circulating air therein and for freezing substances, including a metallic shell,v

a low temperature cooling element disposed in said shell, said shell containing a quantity of liquid refrigerant, and a body of liquid immiscible with said refrigerant contained in said shell and adapted to congeal for maintaining a temperature differential between said shell and said element.

20. The process of refrigeration which comprises, contacting a congealable uid with a volatile liquid refrigerant for congealing at least a 'part of said fiuid, simultaneously condensing the vaporized refrigerant,'returning the condensed refrigerant to the source of liquid refrigerant, and subsequently utilizing the latent heat of fusion of the congealed fluid for condensing the vaporized refrigerant. l

21. Theprocess of refrigeration` which comprises, contacting a liquid with a body of volatile liquid refrigerant, simultaneously condensing the vaporized refrigerant and returning the condensed refrigerant to the liquid, and subsequently utilizing the ice which is frozen by such process as a medium for condensing vaporized refrigerant.

22. The process of refrigeration which comprises, cooling a liquid substance by simultaneously contacting the liquid substance with a bodyyof volatile liquid refrigerant and condensing vaporized refrigerant and returning the condensed refrigerant to the liquidV substance, and subsequently utilizing *thev substance as a medium for condensing vaporized refrigerant. v l l 23. The process of refrigeration which comprises, cooling a liquid which is congealable by cooling 4the same by simultaneously' contacting the liquid with a body of volatile liquid refrigerant and passing the vaporized refrigerant through the congealable liquid and condensing thevacongealable liquid for controlling the vaporization of thel liquid refrigerant.

24. A refrigerating system including a condensing zone and an evaporator zone, a quantity of methylene chloride disposed in said evaporating.

zone, and a body of water floating on the surface of said methylene chloride.

25. Refrigerating apparatus comprising, in combination, `a tank containing a quantity of methylene chloride, a cooling element disposed in the upper part of said tank, a fluid circulating conduit disposed in the lower part of` said tank in contact with said methylene chloride, and a body of water floating upon said methylene chloride for maintaining a. temperature differential between said body of methylene chloride and said element.

26. A cooling unit for refrigerators comprising `two evaporators, one within the other and spaced apart, and means for maintaining a higher temperature within the outer evaporator than within the inner evaporator.

27. A cooling unit for refrigerators comprising an outer flooded evaporator and an inner flooded evaporator arranged within and spaced from said outer evaporator, and means for maintaining said outer evaporator at a temperature higher than the freezing point of water, and for maintaining said inner evaporator at a temperature sufii'ciently low for freezing purposes.

28. A cooling unit for refrigerating machines comprising an outer evaporator, an inner evaporator within and spaced from said outer evaporator, and differential pressure means for maintaining said outer evaporator at a higher temperature than said inner evaporator.

29. A cooling unit for refrigerating machines comprising an outer evaporator and an inner evaporator spaced from said outer evaporator, means for maintaining the temperature of said outer evaporator periodically above and below 32 F., and means for maintaining the temperature o! said inner evaporator suillciently lowfor freezing purposes. y 30. A cooling unit for refrigerating machines comprising an outer evaporator, a second evaporator within and spaced4 from said outer evaporator, means for supplying refrigerant to said second evaporator, means for removing vaporized refrigerant from said second evaporator, and

means including refrigerant flow resistance.

means for maintaining said outer evaporator at a higher temperature than said second evaporator.

.31. In combination, a refrigerator cabinet and a cooling unit within said cabinet and comprising two evaporators, one within the other and spaced apart, and means for maintaining a higher temperature within the outer evaporator than within the inner evaporator.

LAWRENCE A. PHILIPP. 

